Sindra, you and I have come to some pretty similar theories, exactly so in the case of the stop watch and how the Belmonts improved, you're a great writer. I'm creative writing major who loves Castlevania so I put theories to everything, we should talk in pm! I'm going to start a topic I think you'll like called "Story edits" asking how you'd write or re-write the stories of certain games, hope you join in.
Ok... my theories.
First off I believe that Dracula can be resurrected at anytime, but it is times that break the 100 year mark that weaken him, reviving him not at full power. However I do not think he can ever just pop back on his own, as this has never been shown to be the case. It also seems that premature resurrection lengthens the amount of time it takes for him to be revived at full power. Whenever serious strain is put on his spirit it increases the amount of time needed for it to "recharge" so to speak.
I also think that the reason Shanoa is "the only one" who can wield Dominus is because she is either the child or grandchild of Alucard and Maria. I also think Albus is in the same vein as hector or Isaac in terms of how he is different from normal people. If you read the Manga you'll know what I mean. I also wouldn't be surprised if Barlow had some ties to Shaft, i don't think he was ever a good guy.
I would post more, but Sindra you really were very close to most of mine in the questions in this thread. In the case of the Scneider/Morris thing, I just make my Reinhart the first Morris VK wielder in my re-write =) you'll see in the thread. Scneider can be a code name. lol